U.S. patent number 5,332,402 [Application Number 07/881,969] was granted by the patent office on 1994-07-26 for percutaneously-inserted cardiac valve.
Invention is credited to George P. Teitelbaum.
United States Patent |
5,332,402 |
Teitelbaum |
July 26, 1994 |
Percutaneously-inserted cardiac valve
Abstract
A cardiac valve implanted within the heart is given where a
expansible valve maintained in a collapsed form by cold temperature
is percutaneously inserted along a releasable guide wire in a
cooled sheath and when positioned is expanded by withdrawing the
cold temperature.
Inventors: |
Teitelbaum; George P. (Studio
City, CA) |
Family
ID: |
25379601 |
Appl.
No.: |
07/881,969 |
Filed: |
May 12, 1992 |
Current U.S.
Class: |
623/2.42;
623/2.35; 623/900; 623/904 |
Current CPC
Class: |
A61F
2/2409 (20130101); A61F 2/2424 (20130101); A61F
2/2421 (20130101); Y10S 623/90 (20130101); Y10S
623/904 (20130101); A61F 2250/006 (20130101) |
Current International
Class: |
A61F
2/24 (20060101); A61F 002/24 () |
Field of
Search: |
;623/2,900 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Green; Randall L.
Assistant Examiner: Jones; Mary Beth
Attorney, Agent or Firm: Laughlin, Jr.; James H.
Claims
What is claimed is:
1. A method of implanting an expansible cardiac valve within a
heart wherein the expansible cardiac valve is comprised of a
recovery metal having memory and which is capable of expanding to a
desired shape comprising:
releasably coupling a cardiac valve in a compressed form to a
positioning device while maintaining a cool temperature sufficient
to maintain the cardiac valve in said compressed form and which is
capable of passing through heart within which the cardiac valve is
to be implanted;
manipulating the positioning device within the heart so as to
position the cardiac valve at a desired location with the
heart;
ceasing maintaining cool temperature to effect expansion of the
cardiac valve to a desired shape wherein the valve engages the
walls of the heart;
disengaging the positioning device from the expanded cardiac valve;
and
removing the positioning device to leave the cardiac valve
implanted within the heart.
2. The method of claim 1 wherein the cardiac valve comprises a
stent and sliding obturator.
3. The method of claim 1 wherein the cardiac valve comprises stent
and caged ball.
4. The method of claim 1 wherein the cardiac valve expands at about
body temperature.
5. The method of claim 1 wherein the cardiac valve is a mitral
valve.
6. A cardiac heart valve comprising a stent and sliding obturator
formed of a shaped memory alloy which has a transition temperature
of from about 90.degree. to about 96.degree. F.
7. The cardiac heart valve of claim 6 wherein the transition
temperature is about 95.degree. F.
8. A mitral cardiac heart valve comprising a stent and ball and
cage formed of a shaped memory alloy which has a transition
temperature of from about 90.degree. to about 96.degree. F.
Description
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
This invention relates to cardiac valvular surgery techniques for
replacement of diseased cardiac valves. More particularly, this
invention relates to materials and techniques for replacement of
diseased mitral valves in humans as well as other animals.
2. PRIOR ART
Cardiac valvular surgery is performed in cases where there is a
diminished flow area within a cardiac valve which results in a
blockage of normal flow. This blockage leads to cardiac failure.
Cardiac valvular surgery may also be required in cases of valvular
incompetence in which back flow of blood occurs across a valve that
cannot close fully. This is also known as valvular regurgitation
Each of the above conditions are frequently due to rheumatic heart
disease. Replacement of stenotic or narrowed cardiac valves and
regurgitant or incompetent cardiac valves requires open-heart
surgery which utilizes a heart-lung machine.
Expansible devices for implantation have been known by the medical
community. These devices include, for example, the so-called
recovery metals such as titanium-nickel equiatomic intermetallic
compounds which demonstrate mechanical "memory" whereby after being
formed into specific shapes, these metals are compressed or
otherwise given temporary different shapes for insertion and
thereafter, when in place, are expanded whereby their mechanical
"memory" of the originally formed shape causes the device to assume
its originally formed shape.
Materials which are known for having properties useful in such
systems include nickel based alloys such as those described in U.S.
Pat. No. 3,174,851. Typically, these materials comprise 52 to 56
percent nickel by weight with the remainder being titanium. An
initial shape may be permanently set into such recovery metals by
heating them while they are held in the desired configuration. The
forming temperature for setting the initial shape into the
described titanium-nickel alloy is typically about 930.degree. F.
The alloy is then cooled and thereafter deformed plastically to a
deformed configuration which can be retained until the alloy is
reheated to a transition temperature whereafter the alloy will
recover its initial configuration.
Various implantable appliances have been described in the patent
literature. For example, U.S. Pat. No. 3,868,956 uses an expansible
appliance implanted with a vessel through a catheter involving a
positioning device. The positioning device is complex because it
requires the use of electrical conductors to heat the expansible
appliance to allow it to function. U.S. Pat. No. 4,503,569
positions and expands a graft prosthesis using hot saline.
Generally, the known art applies these techniques to the repair of
blood vessels narrowed or occluded by disease.
If a satisfactory means could be devised of replacing diseased
cardiac valves percutaneously, many major open-heart surgeries
could be avoided.
SUMMARY OF THE INVENTION
This invention generally describes a device that serves as a
replacement for a diseased (either stenotic or regurgitant) cardiac
valve. The device is inserted percutaneously via an appropriately
sized small sheath, such as, for example, a 14F sheath using the
jugular venous routes. The sheath is positioned to extend across
the interatrial septum.
The device is fabricated from a "shaped memory" alloy, nitinol,
which is composed of nickel and titanium. Nitinol wire is first
fashioned into the desired shape for the device and then the device
is heat annealed. When the components of the valve are then exposed
to ice-cold temperatures, they become very flexible and supple,
allowing them to be compressed down and pass easily through the
delivery sheath. A cold temperature is maintained within the sheath
during delivery to the deployment site by constantly infusing the
sheath with an iced saline solution. Once the valve components are
exposed to body temperature at the end of the sheath, they
instantaneously reassume their predetermined shapes, thus allowing
them to function as designed.
The percutaneous cardiac valve has two possible designs, each of
which consists of two components. In the first design, one of the
components is a meshwork of nitinol wire of approximately 0.008
inch gauge formed into a tubular structure with a minimum central
diameter of 20 min. Away from its central portion, the tubular
structure flares markedly at both ends in a trumpet-like
configuration. The maximum longitudinal dimension of this component
which shall be referred to as the stent or doubly-flared stent is
approximately 20 mm. The maximum diameter of the flared ends of the
stent is approximately 30 mm. The purpose of the stent is to
maintain a semi-rigid patent channel through the diseased cardiac
valve following its balloon dilation. The flared ends of the stent
maintain the position of this component across the native valve
following deployment. The stent contains a thin hydrophilic plastic
coating that helps prevent thrombus formation along the inner
surface of the stent.
In the second component of the first percutaneous cardiac valve
design is referred to as the sliding obturator. At one end of this
component are two nitinol wires of 0.038 inch diameter which are
fashioned into dual loops a right angles to one another. At the
other end these dual wires are connected to an umbrella-shaped
structure composed of small, thin slats of nitinol metal covered by
silicone rubber with a hydrophilic coating. The dual wires and
umbrella structure can be compressed down so as to fit through a
14F delivery sheath with continuous flushing of this sheath with
ice-cold heparinized saline. When exposed to body temperature at
the end of the delivery sheath, the sliding obturator will expand
to its functional size, with a final umbrella diameter of 20-25
mm.
The sliding obturator will be deployed within the expanded stent.
The loop formed by the dual wires of the sliding obturator will
have sufficient diameter so as not to allow the sliding obturator
being carried away by the force of blood flow. The umbrella portion
of the sliding obturator will flair out so that its widest diameter
will face the interior of the cardiac ventricle. This will allow
the sliding obturator to move forward during diastole (relaxation
of the heart), thus opening the valve and allowing filling of the
ventricle. However, during systole (contraction of the heart), when
there is markedly increased intraventricular pressure, the force of
blood will act against the open or widest portion of the umbrella
pushing back against the flared opening of the wire mesh stent,
thus closing the valve. The sliding obturator will therefore allow
blood flow in only one direction.
The second version of the percutaneous cardiac valve is the ball
design. In this design, the distal end of the wire mesh stent
possesses two curved wires that extend beyond the stent into the
ventricle, forming a cage structure that will house a small
silicone rubber sphere or ball. The silicone sphere will have a
hydrophilic coating to diminish thrombogenicity. The silicone
sphere will be introduced deflated attached to the end of an 8F
catheter through the same delivery sheath used for the placement of
the stent with the distal cage. Once in position within the cage,
the sphere will be inflated with a polymer mixture that will have a
rapid set-up time (it will harden within minutes). After the sphere
has been inflated it will be separated from its delivery catheter
and will remain inflated due to a self-sealing valve at its
attachment point with the delivery catheter. During diastole
(ventricular falling stage), the sphere will be carried forward by
blood flow, thus opening the valve. The cage will act to restrict
the motion of the sphere, preventing it from being lost within the
ventricle. During systole, the sphere will be forced backwards due
to markedly increased intraventricular pressure, thus closing the
valve. The design of the second version of the percutaneous cardiac
valve is similar to the Starr-Edwards cardiac valve which also uses
a ball-valve mechanism to allow only one-way flow through the
valve.
Both versions of the percutaneous cardiac valve are introduced via
the right internal jugular venous approach. Following puncture of
this vein, a catheter and needle combination are used to puncture
the interatrial septum allowing passage of a guide wire and
catheter from the right to the left atrium. The same catheter and
guide wire or catheter is then floated with blood flow out the left
ventricle and into the thoracic aorta. The transjugular guide wire
is then captured by a snare or basket and dragged out through the
right or left common femoral artery. In so doing, one will have
control over both ends of the guide wire used to introduce the
percutaneous cardiac valve. Over this guide wire, a high-pressure
balloon catheter is advanced across the diseased mitral valve where
it is inflated. Once the valve is fully dilated, the balloon
catheter is deflated and replaced with a 14F delivery sheath
inserted via the right internal jugular approach. The sheath's tip
will be positioned in the left ventricle. The nitinol stent (with
or without distal cage) is advanced to the site of the dilated
valve by means of a pusher rod. All the while, the delivery sheath
is being flushed with cold heparinized saline to keep the stent
compressed, soft, and flexible. Once the stent has been pushed to
the distal end of the sheath where it bridges the site of the
dilated valve, the pusher will be held steady while the sheath is
withdrawn, allowing the stent to come into contact with body
temperature. This will cause the rapid expansion of the stent and
create an adequate flow lumen through the diseased valve.
At this point, either the sliding obturator or the silicone sphere
are deployed with the appropriate valve stent. Since both versions
of the stent have a hydrophilic silicone coating, when the sliding
obturator or silicone sphere come into contact with the stent
lumen, they seal or close the valve, preventing backflow of
blood.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cutaway portion of a heart showing the catheter
following a guide wire entering through the interatrial septum.
FIG. 2 is a cutaway portion of a heart showing the stent in place
along the guide wire after the catheter has been withdrawn from the
heart.
FIG. 3 is a cutaway portion of a heart showing the installed
cardiac valve, a sliding obturator, positioned within the
stent.
FIG. 4 is a perspective view of the sliding obturator of this
invention in its expanded and normal form.
FIG. 4A is and FIG. 4B are partial side views of the sliding
obturator of FIG. 4 inserted and in use where FIG. 4A shows its
position within the stent in systole while FIG. 4B shows its
position within the stent in diastole.
FIG. 5 is a perspective view of a different embodiment of this
invention, namely, a ball valve and stent design.
FIG. 6. is a view of the ball of the ball valve of FIG. 5 after
inflation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As noted earlier, cardiac valvular surgery is performed in cases
where there is a diminished flow area within a cardiac valve which
results in a blockage of normal flow which can leads to cardiac
failure. Surgery is often required in cases of valvular
incompetence in which back flow of blood occurs across a valve that
cannot close fully. Replacement of stenotic and regurgitant cardiac
valves can be accomplished in accordance with this invention using
percutaneous techniques allowing for avoidance of many major
open-heart surgery procedures.
This invention describes a device that serves as a replacement for
a diseased stenotic or regurgitant cardiac valve. By this
invention, a technique and the devices which serve as a replacement
for a stenotic or regurgitant diseased cardiac valves is given.
This technique and the devices employed are particularly useful in
replacement of diseased mitral valves.
In this invention, compressed devices are inserted percutaneously
by way of an appropriately sized sheath using the jugular venous
routes and expanded to form new valve mechanisms which provide
replacement cardiac valves.
The catheter and delivery sheath of this invention are
appropriately sized for use. One such appropriate catheter is a 14F
plastic catheter used for delivery and deployment of both stents
and the valve structures of this invention. Such a delivery sheath
is used in the normal matter and may have a pusher capable of
moving a stent or other valve part to its ultimate location in the
heart.
With reference to FIG. 1, FIG. 2 and FIG. 3, in the technique and
procedure of this invention, the percutaneous cardiac valve is
introduced via the right internal jugular venous approach.
Following puncture of this vein, a catheter and needle combination
(not shown) are used to puncture the interatrial septum 4 allowing
passage of a guide wire 8 and catheter 6 from the right to the left
atrium. The same catheter and guide wire or catheter is then
floated with blood flow out the left ventricle and into the
thoracic aorta 10. The transjugular guide wire is then captured by
a snare or basket (not shown) and dragged out through the right or
left common femoral artery. This allows control over both ends of
the guide wire used to introduce the percutaneous cardiac
valve.
Over the guide wire 8, a high-pressure balloon catheter (not shown)
is advanced across the diseased mitral valve where it is inflated.
Once the valve is fully dilated, the balloon catheter is deflated
and replaced with a 14F delivery sheath 6 inserted via the right
internal jugular approach. The sheath's tip will be positioned in
the left ventricle. A compressed nitinol stent, doubly-flared stent
12 as shown, is advanced to the site of the dilated valve by means
of pusher rod (not shown). All the while, the delivery sheath is
being flushed with iced cold heparinized saline to keep the stent
compressed, soft, and flexible. Once the stent has been pushed to
the distal end of the sheath 6 where it bridges the site of the
dilated valve, the pusher will be held steady while the sheath is
withdrawn allowing the stent to come into contact with body
temperature. This will cause the rapid expansion of the stent 12 as
shown in FIG. 2 and create a channel for adequate flow lumen
through the diseased valve.
At this point, a valve mechanism is inserted. While various valve
mechanisms can be employed, this invention is particularly
effective with a sliding obturator 14 position as shown in FIG. 3
and shown in more detail in FIG. 4. Alternatively, a silicone
sphere can be deployed with the appropriate valve stent as shown in
FIG. 5. Since both versions of the stent have a hydrophilic
silicone coating, when the sliding obturator or silicone sphere
come into contact with the stent lumen, a seal is created when the
valve is closed preventing backflow of blood.
The devices of this invention are fabricated from a "shaped memory"
alloy, nitinol, which is composed of nickel and titanium. Nitinol
wire is first fashioned into the desired shape for the device and
then the device is heat annealed. When the components of the valve
are then exposed to ice-cold temperatures, they become very
flexible and supple, allowing them to be compressed down and pass
easily through a delivery sheath. Cold temperature is maintained
with the sheath during delivery to the deployment site by
constantly infusing the sheath with an iced saline solution. Once
the valve components are exposed to body temperature at the end of
the sheath, they instantaneously reassume their predetermined
shapes, thus allowing them to function as designed.
The sliding obturator cardiac valve has two components. As shown in
FIG. 2, one of the components is a stent 12 which comprises a
meshwork of nitinol wire of approximately 0.008 inch gauge formed
into a tubular structure with a minimum central diameter of 20 mm.
Away from its central portion, the tubular structure flares
markedly at both ends in a trumpet-like configuration. The maximum
longitudinal dimension of this stent, or more particularly, a
doubly-flared stent, is approximately 20 mm. The maximum diameter
of the flared ends of the stent is approximately 30 mm. The purpose
of the stent is to maintain a semi-rigid patent channel through the
diseased cardiac valve following its balloon dilation as shown in
FIG. 2. The flared ends of the stent maintain the position of this
component across the native valve following deployment. The stent
contains a thin hydrophilic plastic coating (not shown) that helps
prevent thrombus formation along the inner surface of the
stent.
The second component of the sliding obturator valve design is shown
in FIG. 4. At one end of this component are two nitinol wires of
0.038 inch diameter which are fashioned into dual loops 16 and 18
at right angles to one another. At the other end these dual wires
are connected to an umbrella-shaped structure 20 composed of small,
thin slats of nitinol metal covered by silicone rubber with a
hydrophilic coating. The dual wires and umbrella structure can be
compressed down so as to fit through a delivery sheath with
continuous flushing of this sheath with ice-cold heparinized
saline. When exposed to body temperature at the end of the delivery
sheath, the sliding obturator will expand to its functional size,
with a final umbrella diameter of 20-25 mm.
The sliding obturator will be deployed within the expanded stent as
shown in FIG. 4A and 4B. The loops 16 and 18 formed by the dual
wires of the sliding obturator will have sufficient diameter so as
not to allow the sliding obturator being carried away by the force
of blood flow. The umbrella portion 20 of the sliding obturator
will flair out so that its widest diameter will face the interior
of the cardiac ventricle. This will allow the sliding obturator to
move forward during diastole or relaxation of the heart as shown in
FIG. 4B, thus opening the valve and allowing filling of the
ventricle allowing flow as shown by arrows. However, during systole
or contraction of the heart, when there is markedly increased
intraventricular pressure, the force of blood will act against the
open or widest portion of the umbrella 20 as shown in FIG. 4A
pushing back against the flared opening of the wire mesh stent,
thus closing the valve. The sliding obturator will therefore allow
blood flow in only one direction.
In another embodiment of the percutaneous cardiac valve which may
be used in this invention, a ball design is employed. In this
design as shown in FIG. 5, the distal end of the wire mesh stent
possesses two curved wires 24 and 26 that extend beyond the stent
into the ventricle, forming a cage structure that will house a
small silicone rubber sphere or ball 28. The silicone sphere will
have a hydrophilic coating to diminish thrombogenicity. The
silicone sphere will be introduced deflated (not shown) attached to
the end of a smaller catheter, such as, for example one sized 8F,
through the same delivery sheath used for the placement of the
stent with the distal cage. Once in position within the cage, the
sphere will be inflated with a polymer mixture that will have a
rapid set-up time hardening within minutes. Silicone materials are
well known to be suitable for this purpose. After the sphere has
been inflated as shown in FIG. 6, it will be separated from its
delivery catheter and will remain inflated due to a self-sealing
valve 30 at its attachment point with the delivery catheter. During
diastole or the ventricular filling stage, the sphere will be
carried forward by blood flow, thus opening the valve. The cage
will act to restrict the motion of the sphere, preventing it from
being lost within the ventricle. During systole, the sphere will be
forced backwards due to markedly increased intraventricular
pressure, thus closing the valve. The design of the ball version of
the percutaneous cardiac valve useful in this invention is similar
to the Starr-Edwards cardiac valve which also uses a ball-valve
mechanism to allow only one-way flow through the valve.
Uniquely in this invention, the stent and valves of this invention
are made from a shaped memory nitinol alloy with a transition
temperature in the range of about 90.degree. to about 96.degree. F.
and preferably about 95.degree. F. Those skilled in the art will
appreciate that the transition temperatures of the nitinol family
of alloys can be manipulated over a wide range by altering the
nickel-titanium ratio, by adding small amounts of other elements,
and by varying deformation and annealing processes. Therefore, no
further description of the composition of the shape memory nitinol
alloy is necessary.
In this invention, the cool and cold temperatures used are those
temperatures below about 75.degree. F. In particular, iced-cold
temperatures are generally below about 32.degree. F. and those
skilled in the art will appreciate that the compression
temperatures of the nitinol family of alloys can be manipulated
over a wide range by altering the nickel-titanium ratio, by adding
small amounts of other elements, and by varying deformation and
annealing processes. Therefore, no further description of the
composition of the shape memory nitinol alloy is necessary.
While this invention has been described in its preferred form with
a certain degree of particularity, it is understood that the
present disclosure of the preferred forms and embodiments have been
made only by way of example and that numerous changes in the
details of construction and the combinations and arrangement of
parts may be resorted to without departing from the spirit and the
scope of the invention as claimed.
* * * * *